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Inherited Bleeding Disorders: Learning Objectives

 

Medical Importance

Patients with a wide variety of inherited and acquired bleeding disorders are encountered in nearly all subspecialties of medicine. Most of these disorders can now be identified with appropriate laboratory testing. Screening tests can rapidly distinguish platelet function defects, coagulation disorders and forms of excessive (systemic) fibrinolysis. Assays are also available for most of the components in these pathways, allowing identification of the specific defect in hemostasis. In many cases, the pathogenesis is now understood at a molecular level. With inherited hemorrhagic disorders, accurate diagnosis and understanding of the inheritance is necessary for genetic counseling and identification of family members at risk. Finally, specific therapy is now available for both prophylaxis and treatment of bleeding due to several of these disorders. 

Objectives

  1. Be able to describe five screening tests of hemostasis and list several causes of an abnormal result in each case.
  2. Be able to distinguish between signs and symptoms of primary hemostasis defects and plasma coagulation defects.
  3. Be able to explain why a marked deficiency of von Willebrand factor leads to excessive bleeding.
  4. Recommend two potential forms of therapy for hemorrhage in a patient with type 1 von Willebrand disease and be able to explain a likely mechanism of its therapeutic effect in each case.
  5. Be able to predict the results of hemostatic screening tests (PT/INR, PTT, fibrinogen, platelet count, bleeding time) in a patient with severe hemophilia A.
  6. Explain why a patient with severe von Willebrand disease and a patient with hemophilia A may both have a prolonged PTT.
  7. Using inheritance patterns, clinical history and the results of laboratory tests, be able to distinguish hemophilia A (factor VIII deficiency), hemophilia B (factor IX deficiency) and moderate to severe von Willebrand disease.